181. The most commonly used method for the refining of impure metals is electrolysis.

Answer: Refining

182. After being left in the air for some time, _______ turns black.

Answer: Copper

183. A homogeneous mixture of two or more metals or a metal and a non-metal is called ________.

Answer: Alloy

184. The electrical conductivity and melting point of an alloy is _______ compared to that of a pure metal.

Answer: Lower

185. Non-metals do not _______ displace hydrogen from dilute acids.

Answer: Hydrogen

186. Plaster of Paris is a white powder, and when mixed with water, it turns into ________.

Answer: Gypsum

187. In the chlor-alkali process, _______ gas is given off at the anode.

Answer: Chlorine

188. Aqua regia is a fresh mixture made in the ratio of concentrated hydrochloric acid and concentrated nitric acid of ________.

Answer: 3:1

189. _______ does not react with dilute HCl.

Answer: Copper

190. Ores mined from the earth are generally contaminated with a large quantity of impurities such as soil, sand, etc., which are called ________.

Answer: Gangue

191. Acid + Metal → Salt + _______

Answer: Hydrogen gas

192. Alkalis generate _______ ions in water.

Answer: OH-

193. The pH value decreases.

Answer: Hydronium

194. Present in vinegar.

Answer: Acetic acid

195. When baking soda is heated or mixed with water, _______ is produced, which raises bread or cake and makes them fluffy and soft.

Answer: Carbon dioxide

196. Sulfide ores convert to oxides when heated strongly in the presence of excess air. This process is called _______.

Answer: Roasting

197. An alloy of lead and tin is called.

Answer: Solder

198. Alkaline potassium permanganate or acidified potassium dichromate oxidizes alcohol to _______.

Answer: Aldehyde

199. Alcohol reacts with sodium to produce _______.

Answer: Hydrogen

200. _______ causes blindness by affecting the optic nerve.

Answer: Methanol

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